Three groups of mice congenic at the H-2 locus (a total of 17 strains) are being followed for lifespan/disease patterns to determine the possible influence of the H-2 histocompatibility locus on spontaneous disease, especially cancer. Mice are followed until natural death and subjected to thorough autopsy evaluation. The age-related changes in the immune systems in separate mice of these same strains are being assessed by means of response to mitogens PHA, Con-A, pokeweed, LPS, and PPD, via the mixed-lymphocyte reaction, response to sheep red blood cells, and other methods.